1. Field of the Invention
This invention relates to film-forming compositions of anti-hyperalgesic opiates having substantially no effects on the central nervous system and method of topically treating hyperalgesic conditions.
2. Reported Developments
Pain is the effect of noxious stimuli on nerve endings of a subject which results in the transmission of impulses to the cerebrum. This sensation informs the subject of actual or impending tissue damage and elicits a defensive response. The degree of response substantially correlates with the degree of noxious stimuli in order to speedily avoid further tissue damage and to re-establish normal pre-injury conditions in the subject. The sensation of pain, however, does not end with the stoppage of the noxious stimuli but continues to persist during the inflammation stage of the injury. In turn, the continuation of pain perception causes discomfort to, and deleterously affects the well-being of, the subject. It is, therefore, important to reduce and/or eliminate pain perception of a subject subsequent to injuries.
The reduction/elimination of pain perception can be affected by the central nervous system (hereinafter sometimes referred to as CNS)-mediated analgesia which leads to an overall inhibition of the pain transmission. CNS-mediated analgesia can be effected by systemically administered opiates which, by interaction with specific receptors in the brain and spinal cord, are able to block pain transmission. Systemic opiates, such as morphine, which have been used for many years to control post injury pain, have side effects because their actions within the brain include sedation, depression of respiration, constipation, nausea and development of addiction and dependence. When peripherally applied, opiates have a short duration of action and still possess the undesirable side effects.
Certain opiates, such as loperamide [i.e., 4-(p-chlorophenyl)-4-hydroxy-N-N-dimethyl-.alpha.,.alpha.-diphenyl-1-piper idinebutyramide hydrochloride] and its analogs were reported to be devoid of CNS effects, which is believed to be due to the failure of the opiates to cross the blood brain barrier. Loperamide HCl has been used for a long time in antidiarrheal formulations and has been completely free of the undesirable CNS effects. It would be desirable to use such opiates to inhibit/eliminate post-injury pain without concomitant CNS effects.
It would also be desirable to provide compositions and method for conveniently delivering the compounds to the site of injury.
Therefore, it is an object of the present invention to provide a safe and effective topical composition for inhibiting/eliminating the sensation of pain.
It is another object of the present invention to provide a convenient method of delivering such compositions to the site of injury.
These and other objects are accomplished by delivering a composition to the site of injury, said composition comprising a compound having anti-hyperalgesic activity incorporated in a film-forming composition.